In a hydraulic circuit including a plurality of series-connected valves all supplied by a common source of fluid, the normal method of achieving priority flow to one of the valves ahead of another is to utilize some form of flow divider device such as U.S. Pat. No. 3,229,717. In the present invention, the priority is achieved by separate control of the load check in each valve section. In the valve section claiming priority, the load check can be a conventional type which opens the power passage to one of the motor ports merely by pressure in the power passage. In the non-priority sections, the load checks are opened by pressure build-up piloted from the open-center passages of their particular valve section. When the upstream priority section and non-priority section are actuated, the open-center flow through the valve sections in the stack is blocked causing build-up in the power passage. Since the non-priority section requires pressure in its open-center for fluid to flow to its associated motor, the blockage of the upstream open-center flow by the priority valve prevents the non-priority valve from actuating its motor until the priority valve again opens up the open-center flow.
It is therefore the principal object of the present invention to provide a priority valve section in a stack utilizing conventional valve block castings.
Another object of the invention is to provide a plurality of valve sections in a common stack with the upstream sections always having priority over that section or sections downstream therefrom.